I read many times, that it's recommended to have an ExLink access to TV in order to unbrick it ...
But for my H series UE48H6270, I couldn't find anything helpful how to accomplish this access
I found some information that serial access is still working somehow with H, but w/o info how to do it:

I do NOT support "latest fw" at ALL. If you have one you should block updates on router and wait for it to STOP being "latest":)If you want me to help you please paste FULL log(s) to "spoiler"/"code" bbcodes or provide link(s) to pasted file(s) on http://ctrlv.it/ Otherwise "NO HELP"!!!If you want root DISABLE internet access to your device!!!!DO NOT EVER INSTALL FIRMWARE UPGRADE !!!!

Has anybody done this successfully, i.e. connecting a USB-to-RS232 stick to the TV-USB port, and then having the Top Debug Menu on that serial port???

I read that s.o. wanted to use the same approach to do some home automation, and he probably would be quite angry if suddenly there are a lot of log/error messages on that port, instead of his own automation instructions.

My point of view regarding this approach: 100% for sure there is at least on the mainboard an ExLink port somewhere, and the "TDM" process which is responsible for the Top Debug Menu and the log messages is already connected to that internal serial port.
If I now connect a 2nd serial port to the system, I'm very suspicious that Samsung will launch a 2nd instance of the TDM process which connects to my new 2nd port ... ??? Or that the existing process notice that there is a 2nd port, and magically outputs to both ports and reads from both ports???